1. Field of the Invention
The present invention generally relates to a method of controlling a reflective color of a photonic crystal display device.
2. Description of the Related Art
Reflective display devices that can be driven at low power and can be applied as flexible devices have been intensively researched and developed. An example of such a reflective display device may be an electronic ink, which basically employs a black and white display method and thus requires color filters in order to realize a full-color display device. However, the installation of the color filters causes a decrease in reflectance, resulting in dark colors, difficulty in displaying various colors, a slow color conversion rate, and, therefore, limited capability in displaying moving images.
One of the methods proposed to solve the problems of reflective color display devices of the prior art, is a display method using photonic crystal characteristics of particles dispersed in a medium. A photonic crystal refers to particles or a three-dimensional structure arranged in a medium. The light incident to the photonic crystal is Bragg-diffracted by the three-dimensional structure to reflect only the light of a specific wavelength. The photonic crystal may be used for an electrochromic display device by using a structural feature in which the distance between particles is changed through an electric field. Since the photonic crystal display device requires no color filters for displaying Red, Green, Blue (RGB) full colors and is thin, it can obtain a very high reflectance depending on the manufacturing technique. Therefore, the photonic crystal display device is drawing attention as a core technology for the next-generation display device.
The prior art proposed a technology in which specific-sized particles having surface charges are dispersed in a single solvent to prepare a liquid colloidal photonic crystal, to which an electric field is then applied to control a reflective color. However, in order to display desired ranges of colors in the display device, the size of the photonic crystal particles contained in the colloid should be precisely adjusted during a synthetic procedure of the photonic crystal. Moreover, water used as a single colloidal solvent causes hydrogen to be generated by electrolysis, and causes long-term instability due to its volatility.